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<a name="Environment-Variables"></a>
<h3 class="section">2.2 Environment Variables</h3>


<p>You can change the behaviour of <code>ld</code> with the environment variables
<code>GNUTARGET</code>,
<code>LDEMULATION</code> and <code>COLLECT_NO_DEMANGLE</code>.
</p>
<a name="index-GNUTARGET"></a>
<a name="index-default-input-format"></a>
<p><code>GNUTARGET</code> determines the input-file object format if you don&rsquo;t
use &lsquo;<samp>-b</samp>&rsquo; (or its synonym &lsquo;<samp>--format</samp>&rsquo;).  Its value should be one
of the BFD names for an input format (see <a href="BFD.html#BFD">BFD</a>).  If there is no
<code>GNUTARGET</code> in the environment, <code>ld</code> uses the natural format
of the target. If <code>GNUTARGET</code> is set to <code>default</code> then BFD
attempts to discover the input format by examining binary input files;
this method often succeeds, but there are potential ambiguities, since
there is no method of ensuring that the magic number used to specify
object-file formats is unique.  However, the configuration procedure for
BFD on each system places the conventional format for that system first
in the search-list, so ambiguities are resolved in favor of convention.
</p>
<a name="index-LDEMULATION"></a>
<a name="index-default-emulation"></a>
<a name="index-emulation_002c-default"></a>
<p><code>LDEMULATION</code> determines the default emulation if you don&rsquo;t use the
&lsquo;<samp>-m</samp>&rsquo; option.  The emulation can affect various aspects of linker
behaviour, particularly the default linker script.  You can list the
available emulations with the &lsquo;<samp>--verbose</samp>&rsquo; or &lsquo;<samp>-V</samp>&rsquo; options.  If
the &lsquo;<samp>-m</samp>&rsquo; option is not used, and the <code>LDEMULATION</code> environment
variable is not defined, the default emulation depends upon how the
linker was configured.
</p>
<a name="index-COLLECT_005fNO_005fDEMANGLE"></a>
<a name="index-demangling_002c-default"></a>
<p>Normally, the linker will default to demangling symbols.  However, if
<code>COLLECT_NO_DEMANGLE</code> is set in the environment, then it will
default to not demangling symbols.  This environment variable is used in
a similar fashion by the <code>gcc</code> linker wrapper program.  The default
may be overridden by the &lsquo;<samp>--demangle</samp>&rsquo; and &lsquo;<samp>--no-demangle</samp>&rsquo;
options.
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